forefinger (n.)

"terminal or digital member of the hand" (in a restricted sense not including the thumb), Old English finger, fingor "finger," from Proto-Germanic *fingraz (source also of Old Saxon fingar, Old Frisian finger, Old Norse fingr, Dutch vinger, German Finger, Gothic figgrs "finger"), with no cognates outside Germanic; perhaps ultimately from PIE root *penkwe- "five."

As a unit of measure for liquor and gunshot (late Old English) it represents the breadth of a finger, about three-quarters of an inch. They generally are numbered from the thumb outward, and named index finger, fool's finger, leech- or physic-finger, and ear-finger.

Middle English for-, fore-, from Old English fore-, often for- or foran-, from fore (adv. & prep.), which was used as a prefix in Old English as in other Germanic languages with a sense of "before in time, rank, position," etc., or designating the front part or earliest time.